1. Field of the Invention
The present invention relates to a cable strain relief of the kind having a plurality of conductors which are surrounded by common screen that is embraced by a cable casing and including a sleeve.
The invention also relates to a tool for fitting such a strain relief to a cable of corresponding diameter.
2. Description of the Related Art
A strain relief is a connection element that is coupled to the circumference of a cable and enables forces that act in the length direction of the cable, i.e. axially acting forces, to be transferred to an external construction (e.g. a cable cabinet). Such a cable will normally include a bundle of individual, insulated conductors covered with screen braiding. An insulating sleeve is provided on top of the braiding.
Such strain reliefs will preferably be electromagnetically impervious, i.e. provide electromagnetic insulation (EMI), and must also be capable of transferring forces effectively, so as to prevent individual fibers from being subjected to tensile forces in junction boxes or the like.
A known type of strain relief intended for this purpose is comprised of two tubular parts that have co-acting conical surfaces. One part (the inner part) has slits that extend axially from one end thereof, such as to form axially extending tongues. When the two parts are fitted together axially, the free ends of the tongues will be bent inwardly against the outside of the cable. The outer insulation is removed at the end of the cable and the braiding is folded back around the end of the remaining insulating sleeve. Consequently, when the two tubular parts are fitted together, parts of the braiding threads will be clamped between adjacent tongues. This often results in unsatisfactory anchoring of the strain relief to the cable.
Other known strain reliefs incorporate a U-shaped element whose legs are bent in towards the cable so as to overlap each other. This solution can result in damage to the individual conductors in the cable, and may also cause EMI-leakages to occur through the overlap.
Earlier known strain reliefs are expensive and require the use of complex devices for fitting the reliefs to cables, and also result in joints of greatly differing qualities.